This invention relates to a method for producing a planet carrier for a planetary gear which has a sun gear, one or two ring gears, at least one planetary gear and one input shaft.
Many problems that arise in the operating technology like in transmissions of motor vehicles demand the implementation of extreme ratios. Planetary gears are specially well suited to combine high ratios with a compact design. As an example of this let mention be made of the so-called Wolfrom coupling gear which with a high ratio has high efficiency. A Wolfrom gear is a very simple coupling gear. The input shaft is connected with a sun gear which interacts with a planetary wheel set. The planetary gear set supports itself on an internally toothed ring gear firmly connected with the housing wherein as planet carrier rotates idly. The movement is relayed via the planet carrier and the planetary gear which is designed, for example, as step planet. The planetary gear for its part meshes again with a second internally toothed ring gear which constitutes the output.
Such a planetary gear is adequate for a compact design which on a narrow space permits high transmission densities.
Gears with high ratios are especially needed in handling technology for power transmission of high-speed prime movers. The gears should have, upon a change of load direction, a small torsional play. They must also have an anti-torsional, light and compact structure.
The Applicant""s DE A 195 10 499 has disclosed a planetary gear having a driven sun gear, a first and a second internally toothed ring gear of which the first is stationary and the second is rotationally operable and forms the output, and planetary gears which upon axles that extend slopingly are supported in a planet carrier so as to be in constant tooth contact with the sun gear and the ring gear. The planetary gears are designed as step planets with small and large step wheels, the teeth of the step wheels having different units.
From the Applicant""s DE A 43 25 295 is known another planetary gear having a driven sun gear and two internal ring gears. In this planetary gear the planetary gears, supported on axles in the planet carrier, are disposed slopingly forming an acute angle relative to a central axle of the planetary gear. The planet carrier which here follows idly is supported with low friction via a ball bearing upon a bushing, which bushing abuts, for adjusting the axial position of the planet carrier, on one end via a shoulder on a ball bearing and via a safety ring can be fixed on a spacer disc.
Hereby is created a planetary gear free of play in which can be achieved in the production a great precision which forms the basis for a tight play adjustment.
An essential part of such a planetary gear is the planet carrier which as a rule consists of a forged part and a punched or precision blanked guide plate which are welded with each other. This method of production requires a multiplicity of process steps including an additional welding process.
On account of the distortion of the parts which often occurs during welding, a reprocessing of the planet carrier is needed after the production.
Cast planet carriers have already been used also, but their production requires a likewise high expenditure in processing. To this must be added that the cast molds needed for producing the cast planet carriers have less service life than the shaping tools required for the precision blanking of the guide plates.
The problem on which the invention is based is to provide a method for production of a planet carrier which is considerably easier to carry out so that the costs of production for the planet carrier can be reduced.
It is therefore provided according to the invention that in a press and by means of annular projections, a plurality, preferably two, of guide plates with a number of rivets corresponding to the number of planet gears to be contained be aligned, joined together and riveted with each other in one stroke. The guide plates are here produced as precision blanked parts wherein each of two guide plates situated upon a spider shaft is interconnected with a number of rivets corresponding to the number of planets to be contained by working into the shoulders of the tappets an annular projection concentrically surrounding a longitudinal axle of the rivet bolt; the tool of the press that impinges upon the guide plate in direction of the shoulders is likewise provided with an annular projection which has the same geometry and thus is disposed precisely opposite to the annular projection so that during the rivet upset step no inadmissible deformation of the guide plate occurs outside the annular projection.
The interlinkable joining of the parts in the press creates considerable advantages relative to cost in comparison with the traditional casting and welding methods. One other advantage as to cost results from the fact that chips and the expensive disposal thereof are prevented.
An improvement in quality of the finished planet carrier can be obtained by a clearly small unbalance of the carrier, since it is possible without problem to obtain a riveting of precise position together with an elimination of the great forging tolerances.
Let it be further observed that the inventively produced planet carrier can be designed lighter than the traditional planet carriers whereby a reduction in weight is made possible.